In case of carbon brush electric machines, such as engines, alternators, generators or others, the brushes are pushed against their contact surfaces, such as slip rings or collectors, via a spring. This resilience is required to ensure the engine's proper functioning. In case of the resilience being too high, the brushes and the slip ring or collector wears too quickly (that causes contamination and decreases the insulation resistance). In case of the resilience being too low, bad contact, arcing and degradation due to sparking develops, which leads to damage. If pressure is mutually unequal, the power distribution will become proportionally unbalanced and that, in the first instance, will cause the brushes to wear irregularly and complicate maintenance and, in a further phase, cause some of the brushes to become overloaded and burn with all the associated consequences (could even lead to significant engine damage). It is therefore important to monitor the spring resilience carefully because the spring resilience may start showing signs of deviance after some time due to the temperature, vibrations and even sometimes electrical current that could flow through the springs. It is therefore important to measure the springs and brush pressure regularly.
The best solution for this would be to be able to measure the spring resilience of the carbon brush at its contact surface. However, the space here is extremely limited. The distance between the holder and its contact surface, for example, a slip ring, is firmly set by its required proper operation and accordingly typically ends up being between 2 to 3 mm irrespective of the size of the carbon brush. The spring resilience to be measured depends on the brush size and the application. For example, a traction engine will have a much larger spring resilience than a stationary engine due to the environmental vibrations. Overall, the spring resilience can vary from between 0.1 Kg and 6 Kg. In view of the large variation in the embodiments of the carbon brush holders and the large range of the pressures to be measured, the existing probes are always too large to be able to use them at the ideal places (between the brush and its contact surface, for example, between the brush and the slip ring). The current solutions consist of relatively large probes that always measure the pressure between the carbon brush and the spring resilience system. The range of these probes is frequently limited causing a need for different probes as a function of the pressure to be measured. By moving the measurement of the space between the brush and its contact surface, to the surface between the brush and the spring resilience system, it is sometimes necessary to take the stop angle of the spring resilience system into account in respect of the contact surface between the brush and the slip ring. In case of brushes with oblique heads or oblique holders, the values measured between the brush and pressure resilience system should be converted as function of the angular degrees to eventually be able to get the correct value of the brush contact pressure. Knowing that a single turbo generator of a power station could contain up to 200 brushes, it becomes evident that, in the industry, there is a need for a measuring or pressure sensor that can be deployed between the contact surface and the brush, and where the sensor has a wide pressure range and could therefore be deployed for both stationary and traction engines, alternators and other electrical engines.